What Is A Steam Trap & How Does It Work?

Steam systems are designed to put raw energy to work, and steam traps are a critical part of that system. Truly understanding steam traps requires a little bit of knowledge of steam and condensate, so we’re going to start with the basics.

Steam Traps

Why Steam?

We’re all familiar with the tried and true method of generating energy, pioneered by our apelike ancestors: fire. Fast forward a few hundred years and fire’s still a top choice, but along the way people realized that lighting fires everywhere that energy is needed can create a host of problems. Maintaining a single fire in a controlled, isolated environment is a lot easier – but you can’t send fire down a tube to where it’s needed!  That’s where steam comes into play.  

Steam is capable of holding a lot of energy, travels down tubes on its own, and transfers heat in a uniform fashion- all excellent properties that make it a no-brainer.  The fire takes place in a boiler, which heats water to a boil – converting it into steam.  That steam is distributed to where it’s needed and then some of that energy created in the boiler is harnessed to do work – in things such as radiators, water heaters, industrial kettles, sterilizers, turbines, etc.

Steam Trap

What’s condensate?

When steam energy is harnessed, some of the steam condenses.  For those in the know, let’s forget about conductance, latent heat, sensible heat, saturated steam, and convection for a minute and just bear with this analogy.  Condensate is the ‘sweat’ of steam that’s been put to work.  In other words, steam releases its energy via work and turns back into water.

Steam is good, condensate is inevitable

The excellent properties of steam – it holds a lot of energy, travels down pipes on its own, and transfers heat uniformly – do not apply to water!  Condensate (water) is inevitable when a steam system is doing work, but needs to be taken out of the system so that steam can continue doing its job.  Water also has adverse side effects, such as causing corrosion and water-hammer that we won’t get into here – suffice to say, it’s not wanted in a steam system.

What is a steam trap?

A steam trap is a device that removes condensate from a steam system.  A typical steam system will have many steam traps – they are placed at 50-150’ intervals in straight pipe, after every heat exchanger (where the work gets done), and at every location where there is a change of elevation or pressure.

Steam Traps

What is the purpose of a steam trap?

There are a variety of mechanisms employed by steam traps (click here for an explanation of the four primary types), but they all serve the purpose of keeping steam in the “steam loop” while extracting condensate (and air) and redirecting it to the “condensate loop.” The condensate loop usually feeds into a tank, and from there the water is either processed and returned to the boiler or cooled and discharged as waste.

Steam system operators need to know that their steam traps are doing their job, and decide on size and type based on load levels (min, max, and consistency), cycling requirements, process requirements, longevity, and a plethora of other factors.  For the rest of us, the hope is that we are now armed with sufficient knowledge to dissuade any cavemen we know from lighting more fires – and, more importantly, understand a critical component of systems that play a huge role in our lives in the modern world.

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